Self-adjusting brake



Dec. 22, 1964 D. l. BOHN SELF-ADJUSTING BRAKE Filed April 18, 1963 United States Patent Olitice w 3,162,276 Patented Dec. 22, 1964 3,162,276 SELF-ADJUSTNG BRAKE Donald I. Bohn, Asheville, N11., assignor to 13E-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Apr. 18, 1963, Ser. No. 273,969 9 Claims. (Cl. 188--152) This invention relates to a novel hydraulic brake, and more specically relates to a hydraulic brake which is self-adjusting to have the same opening distance between the brake shoe and drum, regardless of wear on the brake shoe lining. v

Hydraulic brakes are well known for many mechanical applications such as use in cranes and other industrial machinery. One disadvantage of such hydraulic brakes is that as the brake lining wears, the brakes must be fre quently readjusted.

Moreover, the hydraulic systems used normally have points of leakage such as pistons and packings so that periodic bleeding of air is needed.

The principal object of this invention is to provide a novel hydraulic brake which is self-adjusting to automatically compensate for lining wear.

Another object of this invention is to provide a novel hydraulic brake wherein the hydraulic system has no points of leakage so that periodic bleeding of air is not needed.

A further object of this invention is to provide a novel hydraulic brake system wherein the brake shoe and drum form electrical terminals which are connected together when the brake is applied and are disconnected when the brake is released.

These and other objects of this invention will become apparent from the following description when taken in connection with the drawing which shows a side plan view partially in cross-section of the novel self-adjusting hydraulic brake of the invention.

Referring now to the drawing, the brake structure 1 consists of a structural welded base 2 which carries secured-to brake arms 6 and 7 respectively, which are permitted to rotate by a few degrees when the brake is applied and released.

Arms 6 and 7 carry brake shoes 8 and 9 by means of pins 10 and 11. The brake shoes 8 and 9 are so arranged that they are electrically insulated from their respective brake arms 6 and 7. By way of example, suitable insulation bushings 10a and 11a on pins 10 and 11, along with other suitablel washers (not shown) of insulation material can provide an insulated, but pivotal, connection between brake shoes 8 and 9 and their respective operating arms 6 and 7.

The brake shoes 8 and 9 each carry brake linings 12 and 13 respectively, which linings are intended to frictionally engage the surface of the brake drum 14.

In accordance with the invention, the brake linings 12 and 13 are made of a conductive material. By way of example, the brake linings can be suitably formed of asbestos which is interwoven throughout with soft aluminum or copper wire. The brake wheel or drum 14 is of conductive material, whereby tests have shown that when the brake linings 12 and 13 engage drum 14, a relatively low electrical resistance connection is formed between brake shoes 8 and 9 which are normally insulated from one another.

Other suitable brake linings which are sufficiently good electrical conductors are presently commercially available.

The operating mechanism for operating the brake 1 includes a rubber diaphragm-type of pressure unit 15 which is rigidly mounted on channel 16 which is, in turn,

pivotally carried from base 2 by pin 5. The pressure unit 15 may, for example, be of the type known by the name Robotaire Chamber manufactured by the Bendix- Westinghouse Corporation at Elyria, Ohio.

The chamber 15 includes a diaphragm 15a therein which has a rod 15b and an integral pressure plate exthree fulcrum pins 3, 4 and 5 therein. Pins 3 and 4 are l tending therefrom which is attached to the upper end of operating arm 7 through the clevis 7a.

The upper end of channel 16 and, thus, pressure unit 15 which is rigidly clamped to the upper end of channel 16 is connected to operating arm 6 through a rod 17 which is captured between clevises 18 and 19 which are carried by pins 20 and 21 respectively in arms 6 and 16 respectively. The upper ends of operating arms 7 and 16 are then connected together by a tension spring 31.

It can now be seen that when the pressure unit 15 has hydraulic pressure applied on the right-hand side of diaphragm 15a, it will force arm 7 in a counterclockwise direction about pivot 4 and will pull the upper end of arm 6 in a clockwise direction about pin 3 to thereby apply brake shoes 8 and 9 to the brake Wheel 14. The spring 31 is a return spring which opposes this action.

The hydraulic operating system includes a foot pedal which is pivotally mounted on pivot pin 41 of structural member 42 which extends from support frame 43.

Pedal 40 has an extending arm portion 43 which carries a roller 44 which bears against the extending collar 45 of rod 46. The left hand end of rod 46 is secured to the diaphragm 47 of pressure unit 48 where pressure unit 48 is similar in construction to unit 15 except for the arrangement of their operating rods. Pressure unit is carried from extending member 49 of frame 43. A biasing compression spring 50 is then arranged between collar 45 and the housing of unit 48 to bias collar 45 to the right.

The hydraulic system includes an elevated source of fluid 51 which is connected to conduit 52. The end of conduit 52 is connected through a check valve 53 to a conduit 54. Valve 53 permits fluid to low from conduit 52 to conduit 54, but will prevent reverse flow. Conduit 54 is connected to the interior of pressure unit 47 by pipe 55 and is further connected to the Iinlet portion 56 of solenoid valve 57. Solenoid valve 57 has a valve member 58 having a ferromagnetic weight 59 thereon which is contained within solenoid 60. When solenoid 69 is energized, it lifts valve 58 from its blocking position shown to connect inlet portion 56 to conduit 61 leading to the right hand side of diaphragm 15a.

The electrical control circuit for the system includes a conventional A.C. source connected to rectifier transformer 62 which has a single phase bridge connected rectier 63 connected thereto. One terminal of rectifier 63 is connected to lead'64 of solenoid 60. The other terminal of rectifier 63 is connected to the grounded frame 2. Lead 65 of solenoid 60 is connected to shoes 8 and 9 by conductors 66 and 67 so that lead 65 will be grounded to drum 14 when conductive linings 12 and 13 engage drum 14. Thus, when shoes 8 and 9 engage drum 14, solenoid will conduct D.C.V current through the circuit formed between drum 14 and the conductive linings 12 and 13. n

In operation, the hydraulic system is completely filled with an appropriate uid. Assume that the drum 14`is rotating with its shaft 14a, and linings 12 and 13 are held spaced from drum 14. Note that link 68 causes equal spacing of shoes 8 and 9 from drum 14. That is, link 68 is connected between arm 69 secured to pivot rod 4 and collar '70 secured to pivot 3. The manner in which 'this equalization takes place is unimportant to the present invention and is more fully explained in my copending application Serial No. 55,381, iiled September l2, 1960.

In order to apply they pressed t'o movediaphragrn 47 to the left. VrThis forces the iiuid in unit 48 into conduit 54 and intoV inlet 56 of solenoid valve 57. Y Note that checkkvalve 53 prevents fluid iiowinto conduit 52." The uid'entering inlet moves weighted valve 53 upwardlyrsoV the uid enters conduit 61 and moves diaphragm 15a to the left. This moves rod b to -the left and forces arm- 7' counterf clockwise andrarm '6 clockwise (bythe reaction force on pivoted support 16 and rod 17) to move theV brake shoes and linings '12 and 13 into engagement'with drum 14. Once this .engagement occurs, a circuitis completed bea tween D.C. source 63 and solenoidf`60 so that the solenoidy Y 60 holds lvalve 5S open.

When it is desired to release the brake,- the operator releases peda1740, and' spring 31 begins to open brake shoes 8 and 9. fi Fluid can theny flow out yof chamber 15 Vinto conduit l61V and throughconduit 61 valve 57, conduit 54 and into the interior of yunit'48. This iiow of uid continues so long as valve 57 is open whereby the separation of brake liningsIZ and Vliifrom drum 14 Vis determinedrby the length of time valve 58 'is open.

brakes, foot lever 40 is Vde- I between a brake position andreleaseposition withrrespect to* said brake drum;v said electrical circuit means providing current fory saidfsolenoid valve responsive to er1- gagement between said brake shoe lining and said brake drum; .said solenoid valve being open when electrical current iiows thereto and closed when said electrical current l is interrupted; vtime delay means connected tosaid solenoid valve to delay the closing of said solenoid valve, lfor a predeterminedlength ottime after electrical current to said solenoid valve is` interrupted whereby said brake lining has a constant release spacing from said brake 2. The device substantially as set forth vin daim 1 wherein said brake lining is electrically conductive; said brake lining and said drum-f being connected in said electric circuit tqdefin'e va conductive ypath ,to said solenoid while said brake shoe lining engages said brake drum.

l 3. The( devicesubstantially as set forth in claim 2 wherein said hydraulic actuating means comprises a closed hydraulic'system. Y Y f 4 The device substantially as set forth in claim 3 wherein affluid reservoir is connectedy to said hydraulic It will rbe` noted that solenoid 60 is'Y deenergized, as soon as'the brake linings 12 andV 13v leave drum 1411 Therefore, valve 58 Ywill close immediately thereafter or with.

whatever Ytime delay is desiredto have the linings,` 12 and 13 spaced from 'drum 14 with the .desired clearance. Moreover, and in accordance with `the invention, the same Abrake `lining clearance will always be automatically achieved regardless of wear of the linings.

Intentional time delays Aare achieved by appropriately adusting the weight Voi'member 59, or through the use of wellknown shading `coils for solenoid't as-used in A.C. relays. i l y, l

lSince there are nopoints of leakage'in the system, periodic vbleeding of air will not be r1eeded. 'l\/lorev system through a check valve means.v A

5. In combination, a brake drum, a brake shjoe having a brake lining movable between an engaged rand released Vposition with respect to said brake drum, spring biasing means connected to said brake'shoe for biasing said brake'V shoe to said released position, an operating member, ahydraulic actuating system; anda valve; a first portion of said hydraulic actuating system being connected to said operating member; a second portion of said hydraulic system being connected to vsaid brake shoe;

" saidvalve being Vconnected in` said-.hydraulic operating over, reservoir 51 and check valve 53 assure that the system is always full of fluid. Y A

Clearly other check' valve arrangementsl could beused as where the check'valve is opened only when the footlever- 40 is depressed. "Moreover, the checkY valve could be replaced by a ,biased-open valve` member, movable to the closed-position responsive to operation of the foot pedal.V

VVhenit is desired to bushings and a brush on the brake wheelis connectedto one side of the D.C. power source.A YThe other 'D.C. line is then connectedto a terminal of solenoid 60V while the other solenoid terminal is 12 and 13.

use this 'type arrangementdfor a device such as a D.C'. crane, to Vavoid grounding the VD.C. system, the brake wheel is mounted Von insulating connected toy both'` shoesV system in a positionk tocontroluid communication between said first and second portion of rsaid actuating systeinjsa'i'd brake shoe being movable to a released position l'when said valve is opened and,l being stopped'in movelment -When said valve is closed; said'brake shoe lining Av@surface [being operatively connected yto ,said valve and Vmoving said yvalveV toward its'` closed position when said if liningmoves toward said releasedV position; said valve Althoughl have described'rpreferred embedirnentsfoi l mynovel invention, many variations and modifications will now be apparent to those skilled in the art, and I.

prefer therefore to be limited pnotV by the specific dis-` closure herein but only by theappended'rclaims.

'being closed and themovement of said brake shoe being stopped lwhen the surface of said lining moves a predetermined distance from said brake drum; said valve being solenoidl actuated.

' 6'. Thel device as set forth in claim-`5 wherein said brake i shoe lining is electrically conductive. Y

7. The device as set forthV in claim 6 wherein an electric circuit including a voltage source, said brake shoe lining, Vsaidrbrake drum is connected to said solenoid valve whereby said valve is energized and open when said brakeshoe lining engages said brakeV shoe drum.

8..The Vdeviceas set forthV in claim '7' wherein said solenoid valve is closed when saidelectri'c circuit is opened by disengagement-',lbetween said brake shoei liningand '1 said brake drum; andftimedelaymeans fordelaying'tthe The embodimentsof the invention in whichan eXp-- elusive privilege or'property is 'claimed are dened as follows:

1. A seltladjusting hydraulic brake comprising a brake shoe having'ia 1in ing,4fa` brake drum,hydraulic actuating meansconnectedfto said brake shoe, a solenoid valve in y said hydraulic actuatingmeans movable :between *an open?v Y Y' and closcd' 'conditi on, `and electrical circuitmeans con-V nected to saidsolenoid'fvalve, saidbrake shoe'lin'in'gand saidfbrake drum',` said' brake shoelining being movablel closing of saidvalve v after, disengagement between said 9. The device' substantiallyas .set lforth in claimy 5 whereinsaid hydraulic system includes a reservoir connected'theret'o through lcheck yvalve J;neans.,.V

` 2.9.1;,004 Whitten t Nov. 3, 1959v 

1. A SELF-ADJUSTING HYDRAULIC BRAKE COMPRISING A BRAKE SHOE HAVING A LINING, A BRAKE DRUM, HYDRAULIC ACTUATING MEANS CONNECTED TO SAID BRAKE SHOE, A SOLENOID VALVE IN SAID HYDRAULIC ACTUATING MEANS MOVABLE BETWEEN AN OPEN AND CLOSED CONDITION, AND ELECTRICAL CIRCUIT MEANS CONNECTED TO SAID SOLENOID VALVE, SAID BRAKE SHOE LINING AND SAID BRAKE DRUM, SAID BRAKE SHOE LINING BEING MOVABLE BETWEEN A BRAKE POSITION AND RELEASE POSITION WITH RESPECT TO SAID BRAKE DRUM; SAID ELECTRICAL CIRCUIT MEANS PROVIDING CURRENT FOR SAID SOLENOID VALVE RESPONSIVE TO ENGAGEMENT BETWEEN SAID BRAKE SHOE LINING AND SAID BRAKE DRUM; SAID SOLENOID VALVE BEING OPEN WHEN ELECTRICAL CURRENT FLOWS THERETO AND CLOSED WHEN SAID ELECTRICAL CURRENT IS INTERRUPTED; TIME DELAY MEANS CONNECTED TO SAID SOLENOID VALVE TO DELAY THE CLOSING OF SAID SOLENOID VALVE FOR A PREDETERMINED LENGTH OF TIME AFTER ELECTRICAL CURRENT TO SAID SOLENOID VALVE IS INTERRUPTED WHEREBY SAID BRAKE LINING HAS A CONSTANT RELEASE SPACING FROM SAID BRAKE DRUM. 